Apparatus for the simultaneous observation of an incandescent spot and a relatively cool surrounding area



n 1963 R. LEINHOS ETAL APPARATUS FOR THE SIMULTANEOUS OBSERVATION OF ANINCANDESCENT SPOT AND A RELATIVELY COOL SURROUNDING AREA Filed Feb. 6,1961 INVENTORS 1W4 44/17 L M/#08 1 By A; A u s Kac h fl w 4% 1% 44MUnited States Patent 3,02,727 APPARATUS FOR THE SIMULTANEOUS OBSER-VATION OF AN INCANDESCENT SPOT AND A RELATIVELY COOL SURROUNDING AREARoland Leinhos, Oberkochen, Wurttemberg, and Klaus Koch, Aalen,Wurttemberg, Germany, assignors to Carl Zeiss, Oberkochen, Wurttemberg,Germany Filed Feb. 6, 1961, Ser. No. 87,145 Claims priority, applicationGermany Feb. 6, 1960 6 Claims. (Cl. 250-226) This invention relates toapparatus for the simultaneous observation of an incandescent spot and arelatively cool surrounding area.

Apparatus using a charge carrier beam to work material, such as to Weldmaterial, are known to the art. In such machines, the charge carrierbeam is focussed on the material in an impinging beam of small crosssectional area so that the spot on which the beam impinges can be heatedrapidly and to very high temperatures.

The heated material becomes incandescent while the surrounding arearemains dark. The contrast between the incandescent spot and thesurrounding area is of the order of 1110,000.

Both the incandescent spot and the surrounding area must be observed bythe operators to enable the precise control necessary in such operationsas welding of a scam in the material.

In large or inaccessible machines, the observation is usually performedby television camera or a supericonoscope. In such applications the highcontrast ratio precludes the necessary accuracy of observation since theelectron receivers are able to resolve contrast ratios of about 1:30only. Even if the area around the point of contact of the charge carrierbeam is intensely illuminated by light of any spectral composition, thetones of brightness will still be so intense that it cannot bereproduced by the electron receiver. There will also be danger of damage to the photo cathode of the receiver as a result of the very highluminous density of the image of the glowing spot.

It is, therefore, an object of this invention to provide apparatus forthe simultaneous observation of an incandescent spot and the areasurrounding the spot.

In accordance with this object, there is provided, in a preferredembodiment of this invention, a secondary light source of short wavelength to illuminate the area under observation. A filter, passing onlyshort wavelength light, is positioned on the path of the light rays usedfor observation to reduce the contrast ratio to that which can bedisplayed by receivers.

When operating with charge carnier-beam equipment, the temperature ofthe incandescent spot usually ranges upwards to about 3500 C. at thepoint of contact of the beam. The principal emission of the glowingmaterial at the spot to be welded therefore is in the red and infraredregion of the spectrum, while the emission in the blue and violet regionis slight. But the emission of the secondary light source for theillumination lies precisely in the latter region. The filter in the pathof the observation rays passes only shortwave light, i.e. it retainsmost of the radiation emitted by the glowing material, while theabsorption of radiation from the secondary light source is relativelyslight.

Therefore, by appropriate choice of the wave length of the light fromthe secondary light source and of the corresponding filter, the contrastbetween the image of the incandescent spot and the cooler surroundingarea can be established at a prescribed ratio.

The use of a secondary light source emitting a highintensity line in theshortwave region of the spectrum is particularly desirable. For example,a mercury-vapor lamp may be used for illumination, with a blue filterplaced in the observation path. In order to increase the efficiency, aline filter of an interference-layer filter, having a very narrowband-pass, may be used instead of the blue filter. The bandpass of thisfilter would, in this case, correspond to one of the intense lines ofthe mercury vapor lamp, for instance the line 365 mg. or the line 436 myThis new device can be used to particular advantage in carrier beamwelding, using a television camera or a supericonoscope for observationof the work.

A preferred embodiment of this invention is illustrated in theaccompanying FIGURE which is a cross sectional diagrammatic view.

In the figure there is shown an electron-beam generating systemcomprising a cathode 1, control electrode 2, and plate 3. The electronbeam 4 generated by this system passes through the diaphragm 5 and isfocussed by means of the electromagnetic lens 6 on the workpieces 8, 9.The workpieces are clamped on the movable stages 10, 111 in theevacuated chamber 7. The movable stages permit displacement of theworkpieces 8, 9 in two mutually perpendicular directions. In the casehere represented, the two parts 8 and 9 are to be welded together. Forthis purpose the stages 10, 11 must be moved so that the electron beam 4always falls on the seam between the parts 8 and 9.

The work chamber 7 and the beam emission chamber 13 are connected by wayOlf a pump connection 12 to a vacuum pump, which maintains a high vacuumtherein. The work chamber 7 also has 2 other openings, which arehermetically sealed by the glass plates 14 and 15.

The mercury vapor lamp 16 serves to illuminate the workpieces 8, 9, andits light is focussed by the lens 17 on the area adjacent to the pointof contact of the electron beam 4. The light emitted by the part of thematerial under observation is tocussed by the mirrors 18 and 19 and thelenses 20 and 21 on the photocathode of the television camera 22. Theimage may be focussed by vertical displacement of tube 23 and lens 20mounted therein by the externally actuated gear wheel 24.

The rays between the lenses 20 and 21 are parallel.

The blue filter 25 is placed in the parallel rays between the lenses 20and 21. This filter passes, almost completely, the blue portion of thelight emitted by the mercury vapor lamp 16. Consequently theillumination of the area surrounding the point of contact of theelectron beam 4 is attenuated only slightly. 0n the other hand, most ofthe light emitted by the incandescent material being heated by theimpinging electron beam is stopped by the blue filter 25. In this waythe contrast between the hot Workplace and its cold surroundings isreduced to a level no longer critical for television observation.

A line filter or interference-layer filter, which has a very narrowband-pass, may be used instead of the blue filter 25.

Obviously a supericonoscope or any other known electronic image receivermay be substituted for the television camera 22.

This invention can be variously modified and embodied within the scopeof the subjoined claims.

What is claimed is:

'1. Apparatus for simultaneous observation of an incandescent spot andits surroundings, comprising a source of light of short wavelength, saidwave length being shorter than the wave lengths of the principalemission from said incandescent spot, means to focus said light on thearea under observation, said area including said incandescent spot, andmeans for observing said illuminated area, said observation meansincluding a filter passing only light of said short wavelength, saidfilter being placed in the path of the observation rays.

2. Apparatus in accordance with claim 1, in which a television system isused for observation, in which said light source emits a high-intensityline in the shortwave region of the spectrum, and in which said filtercomprises a line filter passing practically only' said line.

3. Apparatus in accordance with claim 2, in which said source comprisesa mercury vapor lamp to illuminate the region under observation and inwhich said filter comprises an interference-layer filter, passing only anarrow band in the region of the lines 436 m or 365 mu.

4. Apparatus in accordance with claim 3, in which said observation meansincludes means to produce an image of the illuminated area of thematerial on the photocathode of the television camera of said televisionsystem.

5. Apparatus in accordance with claim 3, in which 15 4 said observationsystem includes two lenses having a paral- 1el-ray path therebetween andin which said filter is positioned between said two lenses.

6. Apparatus in accordance with claim 1, in which said spot is heated toincandescence -by an impinging chargecarrier beam.

References Cited in the file of this patent UNITED STATES PATENTS 102,046,999 Bredtschneider July 7, 1936 2,178,211 Nolan Oct. 31, 19392,363,270 Smith NOV. 21, 1944 2,465,713 Dimmick Mar. 29, 1949 3,033,974Schleich et al May 8, 1962

1. APPARATUS FOR SIMULTANEOUS OBSERVATION OF AN INCANDESCENT SPOT ANDITS SURROUNDINGS, COMPRISING A SOURCE OF LIGHT OF SHORT WAVELENGTH, SAIDWAVE LENGTH BEING SHORTER THAN THE WAVE LENGTHS OF THE PRINCIPALEMISSION FROM SAID INCANDESCENT SPOT, MEANS TO FOCUS SAID LIGHT ON THEAREA UNDER OBSERVATION, SAID AREA INCLUDING SAID INCANDESCENT SPOT, ANDMEANS FOR OBSERVING SAID ILLUMINATED AREA, SAID OBSERVATION MEANSINCLUDING A FILTER PASSING ONLY LIGHT OF SAID SHORT WAVELENGTH, SAIDFILTER BEING PLACED IN THE PATH OF THE OBSERVATION RAYS.